Electrical switch question

[millinghill]

Hi.

My attic gable fan

a thermostat built in that kicks on when it gets too hot up there. The fan is powered by a dedicated BX cable that runs up to the attic, and this cable has a regular wall switch that I can shut on/off from the 2nd floor hallway. I want the option to run the fan manually too, bypassing the thermostat. I can replace the BX calbe with a

4wire cable (two hot/one neutral/one ground), and have one of the wires bypass the thermostat.

But, what kind of wall switch would I need to buy that has, basically, three settings: off, on (for automatic fan operation via thermostat), and on (for manual operation of fan, bypassing thermostat)?

Advice appreciated. Thanks, Theodore.

[Tony Hwang]

Hi, Jumpering the 'stat with a switch may be the easiest.

[jamesgangnc]

You need a on-off-on three posiiton aka center off switch. Not sure if you can get those with decorator toggles. You might have to get a regular one at radio shack and mount it in a blank faceplate.

You do not need 4 wires from the box to the fan. You only need three, two hots and a neutral. You can use regular 14/3.

You wamt to wire the neutral the way it is now. One of the two hots (black if you use 14/3) will connect the way the existing black hot wire connects. The second hot (red if you use 14/3) would connect to the connection between the thermostat and the fan motor, bypassing the thermostat. On the switch side the original supply hot goes to the center pole. The two hots (balck and red if you use 14/3) to the fan go to the other two switch poles.

Now when the switch is inteh center position the fan is off. In one direction the fan is always on in the other direction the fan is only on if the thermostat calls for it to be on. Test and then label the faceplate.

[N8N]

If you just want "auto/on" a regular light switch will work. If you want a manual off position, you'll need a SPDT switch with a center- off position. Not sure if those are available in a light switch format or if you'd need to use a panel mount toggle and mount it in a hole drilled in a metal blank cover plate.

(firin' up the google machine)

this will work, although not cheap

personally if you need the center off I would spend the bucks for a wall switch... UL listings, code compliance, yadda yadda yadda

nate

[millinghill]

Agreed, but then I'd need two wall switches. Ughh.

[RicodJour]

Who are you quoting here? It's easier to follow a thread if you quote and provide the proper attribution.

Tossing out an idea (that the electrical guru's on this board will either approve or shoot down in flames) - could you use a lighted duplex switch?

If so, it's only the one outlet space and the lighted toggles would tell you at a glance what was controlling the fan.

R

[hrhofmann]

You can get a double-wall switch, easily at almost any place that sells electrical parts, like Home Depot.. Instead of one up-down switch, it has two side-side switches, one above the other in the same space as a regular switch. The cover plate is just a duplex outlet cover plate. I put one in our bathroom, the top switch operates the ceiling light, the lower switch operates the vanity mirror lights. You would wire it up so one switched hot lead goes thru the thermostat, the other switched hot lead goes directly to the motor. if both switches are off, nothing happens. Simple as falling off a log.

[micky]

You can get two toggle switches that fit in a single box. That's what I have for my roof fan.

I can turn it off when the stat would turn it on, or on when the stat would turn it off. I use both features. Normally, when I'm using neither feature, one of the swtiches is Off and one is On so that the stat controls things. Eventually I got confused which position was normal, so I drew a line with an indelible marker across both toggles in their nomarl position.

You would need three conductors from the swtich to the fan/thermostat.

If you're using BX and there's enough room for one more conductor, you could solder one of the conductors that is in there to two new ones, and pull the two through the BX that way. In my house, it's about 8 feet with only a small bit of bending, but be sure to allow a few feeet extra so you don't pull the wires into the BX. Or have a helper or better yet tie a big knot in the wires.

If romex is legal where you are, and the BX isn't stapled inside the wall, you could solder the romex to the BX wires and pull the whole thing through.

[micky]

BTW, how do you expect to do another thing without another swtich?

[micky]

FTR, there is also non-Decora. Standard switches with the normal big handle. I think it's a little easier to see what position the swtich is in when the handle is bigger.

[gfretwell]

You can get a center off SPDT switch in Decora but it is pricy.

[millinghill]

An idea: what if I use a single "three-way switch" and have one hot leg go to the thermostat, and the other hot leg bypass the thermostat? The only downside is that it will never be "off" unless I kill the circuit breaker. Opinions?

[RicodJour]

Why would you want to have to turn off the breaker? Isn't there anything else on that circuit? Using a breaker as a switch is a bad idea, and running an inexpensive fan constantly is also a bad idea.

What's your issue with a lighted (or not) duplex switch?

R

[millinghill]

Exisitng condition is that I can turn fan off with wall switch. Reality is that it is only running when it is too hot (thermostat) in the attic. I would only operate this switch to turn the fan OFF if I need to service the fan or for some emergency. I would *never* use a breaker on a regular (or even irregular) basis as a switch. I think the duplex switch idea is great and will work fine. I'm only asking about the three-way switch idea because I have a box of new ones sitting in the garage right now.

[jamesgangnc]

That's fine. I don't have a switch at all on my attic fan. Lots of them are installed without a switch.

[N8N]

Overkill. You can use a plain old SPDT light switch for the same purpose. You don't actually need to kill the connection through the thermostat when you force the fan on manually.

nate

[millinghill]

Oh I get it now: power always on to thermostat switch, and _bypass_ the thermostat with the manual wall switch! Great. Thanks, Nate and thanks to all others too!!

[clare]

Use 2 switches. One for On/Off and one for Manual/Automatic is the simplest way.

[John Grabowski]

*You could use a combination device with one single pole switch and one three way switch. The single pole would serve as the on-off and the three way will change it from thermostat to always on.

I think this combination is also available in Decora style. Go to an electrical supply company to get one.

[aemeijers]

EVERYTHING should have an off switch. Back in stone age, we would put attic fans and lights on switches mounted too high for kids to reach, right under the scuttle hole. Probably against code now or something. They were not always ivory levitrons, either, for the fans, Some had a very industrial toggle or rotator switch- those were probably for the OTHER kind of attic fan, that sucked hot air out of hallway. Of course, in some old houses, the hallway and gable fans worked in conjunction. Thinking back, that might be a lousy idea in a fire- make the entire house into a chimney. When glowing switches came out, they were very popular for attic lights, so you could tell off or on without opening the hatch again.